A resistive random-access memory (RRAM) is one type of non-volatile memory device which comprises a plurality of memory cells that maintain stored data when power is not supplied. One conventional structure of an RRAM memory cell comprises a metal-insulator-metal (MIM) structure in which the insulator layer (e.g., metal-oxide) exhibits a resistive switching behavior. For example, a RRAM memory cell may exhibit bi-polar switching properties to switch between a high conductivity state (or low resistance state (LRS)) when a first voltage is applied to the memory cell, and a low conductivity state (or high resistance state (HRS)) when a second voltage is applied to the memory cell. In this regard, the two states, LRS and HRS, of the RRAM memory cells are reversible based on the voltage applied thereto.
With resistive memory cells, such as RRAM cells, an “electroforming” process is performed to form a conductive filament in the metal-oxide layer, which serves as a switching element for the memory cell. The electroforming process is performed on newly manufactured memory cells to initialize the resistive switching properties of the memory cells. In general, an electroforming process for a given resistive memory cell comprises applying a voltage pulse to the memory cell at a given voltage level and for a given duration to form a conductive filament in the memory cell. The electroforming process will vary depending on the structural configuration and resistive materials of the resistive memory cells.
RRAM devices typically have low switching resistance (˜kOhm) which results from the formation of a relatively strong conductive filament during the electroforming process. For some applications, however, low switching resistance is not desirable. Therefore, certain techniques can be utilized to control the current that is applied to the memory cells during an electroforming process. For example, in some conventional RRAM frameworks, each RRAM cell comprises a current limiting FET device integrated with the memory cells to limit the amount of current that is applied to the RRAM cells, which poses a significant penalty on the foot print of the memory array.